Such open-end spinning devices are, for example, known from German Patent Publication DE 25 55 059 C2, which discloses a typical open-end spinning unit with a rotor revolving in a rotor housing to which the present invention is applicable. The rotor housing is closed by means of a cover forming a part of a spinning box housing assembly which can be pivoted downward around a pivot shaft for exposing the spinning rotor. In the closed position, i.e. during the spinning process, this housing element is secured by a locking lever.
In this device, the locking lever has a guide surface which is almost concentric in respect to the pivot axis of the housing element and against which a locking roller disposed on the housing element rolls when the housing assembly is pivoted out of its operating position into an unlocking position. In the process, the locking roller maintains the locking lever in the unlocked position, as well as keeping a braking device in a braking position.
The braking device consists of a pivotably seated double lever, which has a brake element at the end of one of its sides. The lever is disposed to be placed on the rotor shaft in the area between the supporting plate bearing wedges. The double lever is furthermore acted upon in the brake release direction by means of a spring element, which acts on the other end of the double lever. The double lever is additionally connected with the locking lever by means of a brake cable such that the brake element is automatically pushed on the rotor shaft when the locking lever is actuated.
Open-end spinning devices designed in this manner are disadvantageous for various reasons. For example, the point of application of the rotor brake between the bearing wedges results in the application of an additional bending moment to the rotor shaft revolving at high rpm. In addition, the danger arises with such a location for applying the brake element that over time the running area of the rotor shaft, i.e. the area in which the rotor shaft rotates on the supporting plates, becomes dirty. It has been shown, in particular with processing synthetic fibers, that over time a mixture of fiber finishes, fiber debris and dust becomes lodged in the area between the running surfaces of the supporting plates and the rotor shaft which can cause an irregular running of the rotor and may have a very disadvantageous effect on the spinning result as well as on the service life of the spinning device.
Therefore a rotor brake has already been proposed in German Patent Publication DE 36 30 256 A1, which avoids the above mentioned problem of the running surfaces becoming soiled. This known rotor brake has a brake shoe arranged between the pairs of supporting plates to be placed from below against the rotor shaft, as well as two hold-down pads which act parallel and can be placed obliquely from above against the rotor shaft in the running area of the supporting plates and the rotor shaft.
All possible deposits are scraped off the rotor shaft in the running area of the rotor shaft by means of the friction of the hold-down pads. Since the rotor is braked after each yarn break, after each bobbin change, and possibly at regularly timed intervals, and since cleaning of the rotor shaft automatically takes place during braking, no more soiling, which would have an interfering effect, can occur at the rotor shaft.
Although the rotor braking device in accordance with German Patent Publication DE 36 30 256 A1 has proven itself in actual use, the device having a brake shoe which can be placed against the rotor shaft from below, as well as two oppositely acting hold-down devices, is very expensive from the viewpoint of its structural design.